Buggy code:
public class RemotingExtension implements Extension { public static final String SUBSYSTEM_NAME = "remoting" ; @ Override public void initialize ( ExtensionContext context ) { } @ Override public void initializeParsers ( ExtensionParsingContext context ) { } static final class NewRemotingSubsystemParser implements XMLStreamConstants , XMLElementReader < List < ModelNode > > , XMLElementWriter < SubsystemMarshallingContext > { private static final RemotingExtension . NewRemotingSubsystemParser INSTANCE = new RemotingExtension . NewRemotingSubsystemParser ( ) ; @ Override public void readElement ( XMLExtendedStreamReader reader , List < ModelNode > list ) throws XMLStreamException { } void parseConnector ( XMLExtendedStreamReader reader , final ModelNode address , final List < ModelNode > list ) throws XMLStreamException { String name = null ; String socketBinding = null ; final EnumSet < Attribute > required = EnumSet . of ( NAME , SOCKET_BINDING ) ; final int count = reader . getAttributeCount ( ) ; for ( int i = 0 ; i < count ; i ++ ) { requireNoNamespaceAttribute ( reader , i ) ; final String value = reader . getAttributeValue ( i ) ; final Attribute attribute = Attribute . forName ( reader . getAttributeLocalName ( i ) ) ; required . remove ( attribute ) ; switch ( attribute ) { case NAME : { name = value ; break ; } case CommonAttributes . SOCKET_BINDING : { socketBinding = value ; break ; } default : throw unexpectedAttribute ( reader , i ) ; } } if ( ! ( required . isEmpty ( ) ) ) { throw missingRequired ( reader , required ) ; } assert name != null ; assert socketBinding != null ; final ModelNode connector = new ModelNode ( ) ; <START_BUG> connector . get ( OP ) . set ( CommonAttributes . ADD_CONNECTOR ) ; <END_BUG> connector . get ( OP_ADDR ) . set ( address ) . add ( CommonAttributes . CONNECTOR , name ) ; connector . get ( CommonAttributes . SOCKET_BINDING ) . set ( socketBinding ) ; final EnumSet < Element > visited = EnumSet . noneOf ( Element . class ) ; while ( ( reader . hasNext ( ) ) && ( ( reader . nextTag ( ) ) != ( XMLStreamConstants . END_ELEMENT ) ) ) { switch ( Namespace . forUri ( reader . getNamespaceURI ( ) ) ) { case REMOTING_1_0 : { final Element element = Element . forName ( reader . getLocalName ( ) ) ; if ( visited . contains ( element ) ) { throw unexpectedElement ( reader ) ; } visited . add ( element ) ; switch ( element ) { case CommonAttributes . SASL : { connector . get ( CommonAttributes . SASL ) . set ( parseSaslElement ( reader ) ) ; break ; } case CommonAttributes . PROPERTIES : { parseProperties ( reader , connector . get ( CommonAttributes . PROPERTIES ) ) ; break ; } case CommonAttributes . AUTHENTICATION_PROVIDER : { connector . get ( CommonAttributes . AUTHENTICATION_PROVIDER ) . set ( readStringAttributeElement ( reader , "name" ) ) ; break ; } default : { throw unexpectedElement ( reader ) ; } } break ; } default : { throw unexpectedElement ( reader ) ; } } } list . add ( connector ) ; } ModelNode parseSaslElement ( final XMLExtendedStreamReader reader ) throws XMLStreamException { } ModelNode parsePolicyElement ( XMLExtendedStreamReader reader ) throws XMLStreamException { } void parseProperties ( XMLExtendedStreamReader reader , final ModelNode node ) throws XMLStreamException { } @ Override public void writeContent ( XMLExtendedStreamWriter writer , SubsystemMarshallingContext context ) throws XMLStreamException { } private void writeConnector ( final XMLExtendedStreamWriter writer , final ModelNode node , final String name ) throws XMLStreamException { } private void writeProperties ( final XMLExtendedStreamWriter writer , final ModelNode node ) throws XMLStreamException { } private void writeSasl ( final XMLExtendedStreamWriter writer , final ModelNode node ) throws XMLStreamException { } private void writePolicy ( final XMLExtendedStreamWriter writer , final ModelNode node ) throws XMLStreamException { } private boolean has ( ModelNode node , String name ) { } private void writeAttribute ( final XMLExtendedStreamWriter writer , final Attribute attr , final ModelNode value ) throws XMLStreamException { } private void writeSimpleChild ( final XMLExtendedStreamWriter writer , final Element element , final Attribute attr , final ModelNode value ) throws XMLStreamException { } } private static class RemotingSubsystemDescribeHandler implements ModelQueryOperationHandler , DescriptionProvider { static final RemotingExtension . RemotingSubsystemDescribeHandler INSTANCE = new RemotingExtension . RemotingSubsystemDescribeHandler ( ) ; @ Override public OperationResult execute ( final OperationContext context , final ModelNode operation , final ResultHandler resultHandler ) { } @ Override public ModelNode getModelDescription ( Locale locale ) { } } }

Fix:
connector . get ( OP ) . set ( ADD ) ;